From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Experiments comparing a Bosch armature with an in-house motor, detailing operational failures and noise issues.
| Identifier | WestWitteringFiles\T\November1928\ Scan093 | |
| Date | 17th December 1928 | |
| EFCL/T17.12.28. -5- Contd. You will remember that the Bosch armature is parallel and that the spring is a very long one with a low rating but well set up. We are comparing the relation of longitudinal pull to travel in the cases of this Bosch motor and our own motor. We are enthusiastically experimenting when possible. We think we have now overcome, but have had in view in the first instance, the elimination of the complete failure to operate in any circumstances, i.e. (a) Failure of armature to start out. (Scarcely ever now occurs but may when very cold). (b) Failure of armature to return from corner jamming to give driver a second opportunity. (This has been usually due to eliminatable frictional effect). Then there is the partial failure of corner jamming. i.e. failure on first (or subsequent) press of button only. which we hope in time to eliminate.. Particularly there remain the noise difficulties, even when the operation is O.K.. these being - (1) Slight thump on engagement, which, however, is largely reduced by the use of a spring of a suitably chosen rating between the two extremes of weak and strong. The engaging thump does not appear to be materially affected by switching on the main current, and this would be explained by the fact that the main current does not produce appreciably more longitudinal pull than the tapper current; also possibly by the fact that the resistance to longitudinal motion would be increased by the pressure on the teeth. Our tests have shown that the timing of the armature operated switching contact is uncritical. Contd. | ||